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  • 1.
    Adamczyk, Krzysztof
    et al.
    Department of Materials Science and Engineering, Trondheim, Norway.
    Søndenå, Rune
    Department for Solar Energy, IFE, Kjeller, Norway.
    Stokkan, Gaute
    Sintef Materials and Chemistry, Trondheim, Norway.
    Looney, Erin
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Jensen, Mallory
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Lai, Barry
    Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Di Sabatino, Marisa
    Department of Materials Science and Engineering, NTNU, A. Getz vei 2B, NO-7491 Trondheim, Norway.
    Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing2018In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 5, p. 1-6, article id 055705Article in journal (Refereed)
    Abstract [en]

    In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

  • 2.
    Adamczyk, Krzysztof
    et al.
    Department of Materials Science and Engineering, Trondheim, Norway.
    Søndenå, Rune
    Department for Solar Energy, IFE, Kjeller, Norway.
    You, Chang Chuan
    Department for Solar Energy, IFE, Kjeller, Norway.
    Stokkan, Gaute
    Sintef Materials and Chemistry, Trondheim, Norway.
    Lindroos, Jeanette
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Di Sabatino, Marisa
    Department of Materials Science and Engineering, Trondheim, Norway.
    Recombination Strength of Dislocations in High-Performance Multicrystalline/Quasi-Mono Hybrid Wafers During Solar Cell Processing2018In: Physica Status Solidi (a) applications and materials science, ISSN 1862-6300, E-ISSN 1862-6319, Vol. 215, no 2, article id 1700493Article in journal (Refereed)
    Abstract [en]

    Wafers from a hybrid silicon ingot seeded in part for High Performance Multicrystalline, in part for a quasi-mono structure, are studied in terms of the effect of gettering and hydrogenation on their final Internal Quantum Efficiency.The wafers are thermally processed in different groups – gettered and hydrogenated. Afterwards, a low temperature heterojunction with intrinsic thin layer cell process is applied to minimize the impact of temperature. Such procedure made it possible to study the effect of different processing steps on dislocation clusters in the material using the Light Beam Induced Current technique with a high spatial resolution. The dislocation densities are measuredusing automatic image recognition on polished and etched samples. The dislocation recombination strengths are obtained by a correlation of the IQE with the dislocation density according to the Donolato model. Different clusters are compared after different process steps. The results show that for the middle of the ingot, the gettering step can increase the recombination strength of dislocations by one order of magnitude. A subsequent passivation with layers containing hydrogen can lead to a decrease in the recombination strength to levels lower than in ungettered samples.

    The full text will be freely available from 2018-11-07 16:03
  • 3.
    Andersson, Stig
    et al.
    Göteborgs Universitet.
    Svensson, Krister
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Excitation and desorption of physisorbed H2 via the 2Σu electron scattering resonance.2017In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 147, p. 114703-1-114703-11, article id 114703Article in journal (Refereed)
    Abstract [en]

    Our high-resolution electron energy-loss measurements concern physisorbed H2 and comprise dif- ferential cross sections for the excitation of the internal H2 modes and the H2-surface bonding mode and their combinations and extend over the electron impact energy range of the classical low-energy H2 2Σu resonance. Comparison with corresponding data for the excitation of the internal modes of gas phase H2 reveals that strong elastic electron reflectivity from the Cu(100) substrate profoundly distorts the inelastic scattering pattern for physisorbed H2. We find that this influence can be corrected for and that the resulting peak cross sections agree with the H2 gas phase data, in accordance with theoretical predictions for the excitation of the internal H2 vibration. We have used corrected cross sections for the rotational mode spectra of physisorbed H2, HD, and D2 in a model concerning elec- tron induced desorption via rotation-translation energy conversion. These spectra include transitions from the ground state as well as excited levels of the physisorption potential well. H2 and HD can desorb from all levels while D2, for energetic reason, can only desorb from the excited levels. This model gives a satisfactory account of the observed desorption cross sections and predicts character- istic velocity distributions of the desorbing molecules. The cross section data for H2 and HD reveals that direct bound-free transitions also contribute to the electron induced desorption. 

  • 4.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Characterisation of vertical phase separation in polymer: fullerene blend films for photovoltaics by dSIMS and NEXAFS2011In: E-MRS 2011 Spring Meeting: Bilateral Energy Conference, Malden, MA: John Wiley & Sons, 2011, p. 62-63Conference paper (Refereed)
    Abstract [en]

    Morphological control and characterization of blend films is key in the development of viable polymer solar cells. Spontaneous formation of vertical compositional gradients during solution processing has been shown for polyfluorene:PCBM blends and rationalized with thermodynamic and kinetic models of nucleation and spinodal decomposition.[1, 2] The extent of vertical stratification is affected by polymer side-chain modification aimed at controlling polymer:fullerene miscibility.[3] Here we present high-resolution film morphology results for several polymer:fullerene systems as obtained from near-edge X-ray fine structure spectroscopy (NEXAFS) in partial and in total electron yield modes. Blend films were found to be polymer- enriched at the surface. Dynamic secondary ion mass spectrometry (dSIMS) and NEXAFS give compositional information at different depths, resulting in a more complete picture of the film morphology.

     

  • 5.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Polymer solar cells: Visualizing vertical phase separation in solution-processed films of polymer fullerene blends2012In: Proceedings of the 5th International Symposium Technologies for Polymer Electronics - TPE 12 / [ed] Hans-Klaus Roth, Klaus Heinemann, Ilmenau, Germany: Universitätsverlag Ilmenau , 2012, p. 125-128Conference paper (Refereed)
  • 6.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wang, Ergang
    Chalmers University of Technology.
    Andersson, Mats R.
    Chalmers University of Technology.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Molecular orientation and composition at the surface of APFO3:PCBM blend films2012In: Hybrid and Organics Photovoltaics Conference: Uppsala, Sweden, 2012 / [ed] Anders Hagfeldt, SEFIN, Castelló (Spain), 2012, p. 278-Conference paper (Refereed)
  • 7.
    Asker, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Axion Electrodynamics and Measurable Effects in Topological Insulators2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Topological insulators are materials with their electronic band structure in bulk resembling that of an ordinary insulator, but the surface states are metallic. These surface states are topologically protected, meaning that they are robust against impurities. The topological phenomena of three dimensional topological insulators can be expressed within topological field theories, predicting axion electrodynamics and the topological magnetoelectric effect. An experiment have been suggested to measure the topological phenomena. In this thesis, the underlying theory and details around the experiment are explained and more detailed derivations and expressions are provided.

  • 8.
    Bertoni, M. I.
    et al.
    Massachusetts Institute of Technology, Cambridge, USA .
    Fenning, D. P.
    Massachusetts Institute of Technology, Cambridge, USA .
    Rinio, Markus
    Fraunhofer ISE, Laboratory and Servicecenter, Auf der Reihe 2, Gelsenkirchen, Germany .
    Rose, V.
    USA.
    Holt, M.
    USA.
    Maser, J.
    USA.
    Buonassisi, Tonio
    USA.
    Nanoprobe X-ray fluorescence characterization of defects in large-area solar cells2011In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 4, p. 4252-4257Article in journal (Refereed)
    Abstract [en]

    The performance of centimeter-sized energy devices is regulated by inhomogeneously distributednanoscale defects. To improve device efficiency and reduce cost, accurate characterization of thesenanoscale defects is necessary. However, the multiscale nature of this problem presentsa characterization challenge, as non-destructive techniques often specialize in a single decade of lengthscales, and have difficulty probing non-destructively beneath the surface of materials with sub-micronspatial resolution. Herein, we push the resolution limits of synchrotron-based nanoprobe X-rayfluorescence mapping to 80 nm, to investigate a recombination-active intragranular defect in industrialsolar cells. Our nano-XRF measurements distinguish fundamental differences between benign anddeleterious dislocations in solar cell devices: we observe recombination-active dislocations to containa high degree of nanoscale iron and copper decoration, while recombination-inactive dislocationsappear clean. Statistically meaningful high-resolution measurements establish a connection betweencommercially relevant materials and previous fundamental studies on intentionally contaminatedmodel defect structures, pointing the way towards optimization of the industrial solar cell process.Moreover, this study presents a hierarchical characterization approach that can be broadly extended toother nanodefect-limited energy systems with the advent of high-resolution X-ray imaging beamlines

  • 9.
    Björström Svanström, Cecilia M.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    Institute of Physics, Jagiellonian University, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Poland.
    Budkowski, Andrzej
    Institute of Physics, Jagiellonian University, Poland.
    Zhang, Fengling
    nic Electronic (COE), Linköping University, Sweden.
    Inganäs, Olle
    IFM and Center of Organic Electronic (COE), Linköping University, Sweden.
    Andersson, Mats R.
    Department of Chemical and Biological Engineering, Chalmers University of Technology.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Benson-Smith, Jessica
    Department of Physics, Imperial College, London, U.K..
    Nelson, Jenny
    Department of Physics, Imperial College, London, U.K..
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Device performance of APFO-3/PCBM solar cells with controlled morphology2009In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 21, no 43, p. 4398-4403Article in journal (Refereed)
    Abstract [en]

    Polymer/fullerene solar cells with three different device structures: A) diffuse bilayer, B) spontaneously formed multilayer, and C) vertically homogenous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency.

  • 10.
    Blazinic, Vanja
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Muntean, Stela Andrea
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Photo-degradation in air of spin-coated PC60BM and PC70BM films2018In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 241, p. 26-30Article in journal (Refereed)
    Abstract [en]

    The fullerene derivatives PC60BM and PC70BM are widely used as electron accepting components in the active layer of polymer solar cells. Here we compare their photochemical stability by exposing thin films of PC60BM and PC70BM to simulated sunlight in ambient air for up to 47 h, and study changes in their UV–vis and FT-IR spectra. We quantify the photo-degradation by tracking the development of oxidation products in the transmission FT-IR spectra. Results indicate that PC60BM photodegrades faster than PC70BM. The rate of photo-oxidation of the thin films is dependent on the rate of oxygen diffusion in to the film and on the photo-oxidation rate of a single molecule. Both factors are dependent on the nature of the fullerene cage. The faster photo-oxidation of PC60BM than of PC70BM is in agreement with its slightly lower density and its higher reactivity. The use of PC70BM in solar cells is advantageous not only because of its absorption spectrum, but also because of its higher stability.

    The full text will be freely available from 2020-04-07 11:29
  • 11. Borchert, Dietmar
    et al.
    Brammer, T.
    Voigt, O.
    Stiebig, H.
    Gronbach, A.
    Rinio, Markus
    Kenanoglu, A.
    Willeke, G.
    Nositschka, A.
    Kurz, H.
    Large area (N) A-Si:H/(P) C-Si heterojunction solar cells with low temperature screen printed contacts2004Conference paper (Other academic)
  • 12. Borchert, Dietmar
    et al.
    Gronbach, Andreas
    Rinio, Markus
    Zippel, Elmar
    Process steps for the production of large area (n) a-Si:H/(p) C-Si heterojunction solar cells2005Conference paper (Other academic)
  • 13. Borchert, Dietmar
    et al.
    Gronbach, Andreas
    Schaefer, B.
    Rinio, Markus
    Abusnina, Mohammed
    Kenanoglu, Ali
    Willeke, Gerhard
    Large area RF deposition of thin films for silicon solar cells2004Conference paper (Other academic)
  • 14. Borchert, Dietmar
    et al.
    Hanke, Martin
    Ban, Q.
    Schmidt, K.
    Rinio, M.
    Microcrystalline silicon films as active layers in crystalline silicon solar cells2006Conference paper (Other academic)
  • 15.
    Borchert, Dietmar
    et al.
    Fraunhofer ISE, Laboratory and Servicecenter Gelsenkirchen,.
    Rinio, Markus
    Fraunhofer ISE, Laboratory and Servicecenter Gelsenkirchen,.
    Interaction between process technology and material quality during the processing of multicrystalline silicon solar cells2009In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 20, no 1, p. 487-492Article in journal (Refereed)
    Abstract [en]

    Multicrystalline silicon is the most used materialfor the production of silicon solar cells. The quality of the asgrown material depends on the quality of the feedstock andthe crystallization process. Bulk impurities, crystal defectslike dislocations and of course the grain boundaries determinethe material quality and thus the solar cell conversionefficiency. Therefore minority carrier lifetime measurementsare often done to characterize the material quality. Butthe measured values are from limited use because it is knownthat the solar cell process itself can dramatically change theminority carrier lifetime and the solar cell efficiency. In orderto obtain more detailed information of the behaviour ofdifferent defect types additionally high-resolution LBIC(light beam induced current)-measurements have been done.Since LBIC needs a pn-junction for photocurrent generationthe LBIC technique has been combined with the a-Si/c-Siheterojunction cell process, which makes it possible tomanufacture solar cells even from as cut wafers withoutchanging the material quality. With this combination ofmeasurement and preparation techniques it was possible toanalyze the influence of the diffusion process and the firingprocess on the behaviour of the three different defect types: grain boundaries, dislocation networks and bulk impurities.

  • 16. Borchert, Dietmar
    et al.
    Rinio, Markus
    Tölle, R.
    Janßen, Lars
    Nositschka, W. A.
    Kurz, H.
    Silicon nitride for backside passivation of multicrystalline solar cells2005Conference paper (Other academic)
  • 17.
    Boulfrad, Yacine
    et al.
    Aalto University.
    Lindroos, Jeanette
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics. Aalto University.
    Inglese, Alessandro
    Aalto University.
    Yli-Koski, Marko
    Aalto University.
    Savin, Hele
    Aalto University.
    Reduction of Light-induced Degradation of Boron-doped Solar-grade Czochralski Silicon by Corona Charging2013In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 38, p. 531-535Article in journal (Refereed)
    Abstract [en]

    Abstract This study aims at the reduction of light-induced degradation of boron-doped solar-grade Czochralski silicon wafers by corona charging. The method consists of deposition of negative charges on both surface sides of wafer and keeping the wafer in dark for 24 hours to allow the diffusion of positively-charged interstitial copper towards the surfaces. This method proves to be useful to reduce or eliminate light-induced degradation caused by copper. The degradation was significantly reduced in both intentionally (copper-contaminated) and “clean” samples. The amount of the negative charge was found to be proportional to the reduction strength

  • 18.
    Boulfrad, Yacine
    et al.
    Finland.
    Lindroos, Jeanette
    Department of Micro- and Nanosciences, Aalto University, Finland.
    Wagner, Matthias
    Germany.
    Wolny, Franziska
    Germany.
    Yli-Koski, Marko
    Finland.
    Savin, Hele
    Finland.
    Experimental evidence on removing copper and light-induced degradation from silicon by negative charge2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 18, article id 182108Article in journal (Refereed)
  • 19. Breitenstein, Otwin
    et al.
    Langenkamp, Martin
    McIntosh, K. R.
    Honsberg, C. B.
    Rinio, Markus
    Localization of shunts across the floating junction of DSBC solar cells by lock–in thermography2001Conference paper (Other academic)
  • 20.
    Brumboiu, Iulia Emilia
    et al.
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    Ericsson, Leif K.E.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    Brena, Barbara
    Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden.
    The influence of oxygen adsorption on the NEXAFS and core-level XPS spectra of the C60 derivative PCBM2015In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 142, p. 054306-Article in journal (Refereed)
  • 21.
    Budkowski, Andrzej
    et al.
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lekka, M
    The Henryk Niewodnicza¶nski Institute of Nuclear Physics Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krakow, Poland.
    Zemla, J
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Jaczewska, Justyna
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Haberko, Jakub
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Raczkowska, Joanna
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Rysz, Jakub
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Awsiuk, K
    M. Smoluchowski Institute of Physics and Research Centre for Nanometer-Scale Science and Advanced Materials (NANOSAM) Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland.
    Structures in multi-component polymer films: their formation, observation and applications in electronics and biotechnology2009In: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Proceedings of the XLII Zakopane School of Physics, Zakopane 2008, Vol. 115, no 2, p. 435-440Article in journal (Refereed)
    Abstract [en]

    Several strategies to form multicomponent films of functional polymers, with micron, submicron and nanometer structures, intended for plastic electronics and biotechnology are presented. These approaches are based on film deposition from polymer solution onto a rotating substrate (spin-casting), a method implemented already on manufacturing lines. Film structures are determined with compositional (nanometer) depth profiling and (submicron) imaging modes of dynamic secondary ion mass spectrometry, near-field scanning optical microscopy (with submicron resolution) and scanning probe microscopy (revealing nanometer features). Self-organization of spin-cast polymer mixtures is discussed in detail, since it o®ers a one-step process to deposit and align simultaneously domains, rich in di®erent polymers, forming various device elements: (i) Surface segregation drives self-stratification of nanometer lamellae for solar cells and anisotropic conductors. (ii) Cohesion energy density controls morphological transition from lamellar (optimal for encapsulated transistors) to lateral structures (suggested for light emitting diodes with variable color). (iii) Selective adhesion to substrate microtemplates, patterned chemically, orders lateral structures for plastic circuitries. (iv) Submicron imprints of water droplets (breath figures) decorate selectively micron-sized domains, and can be used in devices with hierarchic structure. In addition, selective protein adsorption to regular polymer micropatterns, formed with soft lithography after spin-casting, suggests applications in protein chip technology. An approach to reduce lateral blend film structures to submicron scale is also presented, based on (annealed) films of multicomponent nanoparticles

  • 22.
    Budkowski, Andrzej
    et al.
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Zemla, Joanna
    Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Awsiuk, Kamil
    Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Bernasik, Andrzej
    Faculty of Physics and Applied Computer Science, AGH-University of Science and Technology, Al. Mickiewicza 30, Krakow 30–059, Poland.
    Björström Svanström, Cecilia M.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lekka, Małgorzata
    Niewodniczanski Institute of Nuclear Physics, Polish Academy of Science, Krakow, Poland.
    Jaczewska, Justyna
    Institute of Physics, Jagiellonian University, Krakow, Poland.
    Polymer Blends Spin-Cast into Films with Complementary Elements for Electronics and Biotechnology2012In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Special Issue: Contributions from the 4th International Conference on Polymer Behavior (IUPAC), Lodz, Poland, September 19–23, 2010, Vol. 125, no 6, p. 4275-4284Article in journal (Refereed)
    Abstract [en]

    Versatility of solution-processing strategy based on the simultaneous rather than additive deposition of different functional molecules is discussed. It is shown that spin-cast polymer blends result in films with domains that could form elements with complementary functions of (i) solar cells, (ii) electronic circuitries, and (iii) test plates for protein micro-arrays: Alternating layers, rich in electrondonating polyfluorene and electron-accepting fullerene derivative, result in optimized solar power conversion. Surface patterns, made by soft lithography, align conductive paths of conjugated poly(3-alkylthiophene) in dielectric polystyrene. Proteins, preserving their biologically activity, are adsorbed to hydrophobic domains of polystyrene in hydrophilic matrix of poly(ethylene oxide). The authors report the research progress on structure formation in three polymer blend families, resulting in films with complementary elements for electronics and biotechnology. Blend film structures are determined with secondary ion mass spectrometry, atomic force microscopy, and fluorescence microscopy. In addition, the authors present recent results on (i) structure formation in fullerene derivative/poly(3-alkylthiophene) blends intended for solar cells, (ii) 3-dimensional SIMS imaging of conductive paths of poly(3-alkylthiophene) in dielectric polystyrene, (iii) test lates for multiprotein micro-arrays fabricated with blend films of hydrophobic polystyrene and thermoresponsive poly (N-sopropylacrylamide).

  • 23.
    Castellanos, Sergio
    et al.
    Massachusetts Institute of Technology, Camebridge, MA, USA.
    Hofstetter, Jasmin
    Massachusetts Institute of Technology, Camebridge, MA, USA.
    Kivambe, Maulid
    Massachusetts Institute of Technology, Camebridge, MA, USA.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Lai, Barry
    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois, USA.
    Buonassisi, Tonio
    Massachusetts Institute of Technology, Camebridge, MA, USA.
    Inferring Dislocation Recombination Strength in Multicrystalline Silicon via Etch Pit Geometry Analysis2014Conference paper (Other academic)
    Abstract [en]

    Dislocations limit solar cell performance bydecreasing minority carrier diffusion length, leading to inefficientcharge collection at the device contacts. However, studieshave shown that the recombination strength of dislocationclusters within millimeters away from each other can vary byorders of magnitude. In this contribution, we present correlations between dislocation microstructure and recombination activity levels which span close to two orders of magnitude. We discuss a general trend observed: higherdislocation recombination activity appears to be correlated witha higher degree of impurity decoration, and a higher degree ofdisorder in the spatial distribution of etch pits. We present anapproach to quantify the degree of disorder of dislocationclusters. Based on our observations, we hypothesize that therecombination activity of different dislocation clusters can bepredicted by visual inspection of the etch pit distribution andgeometry.

  • 24.
    Castellanos, Sergio
    et al.
    Massachusetts Institute of Technology, Massachusetts, USA.
    Kivambe, Maulid
    Massachusetts Institute of Technology, Massachusetts, USA.
    Hofstetter, Jasmin
    Massachusetts Institute of Technology, Massachusetts, USA.
    Rinio, Markus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Lai, Barry
    Argonne Photon Source, Illinois, USA.
    Buonassisi, Tonio
    Massachusetts Institute of Technology, Massachusetts, USA.
    Variation of dislocation etch-pit geometry: An indicator of bulk microstructure and recombination activity in multicrystalline silicon2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 18, p. 183511-1-183511-7, article id 183511Article in journal (Refereed)
    Abstract [en]

    Dislocation clusters in multicrystalline silicon limit solar cell performance by decreasing minoritycarrier diffusion length. Studies have shown that the recombination strength of dislocation clusterscan vary by up to two orders of magnitude, even within the same wafer. In this contribution, wecombine a surface-analysis approach with bulk characterization techniques to explore theunderlying root cause of variations in recombination strength among different clusters. We observethat dislocation clusters with higher recombination strength consist of dislocations with a largervariation of line vector, correlated with a higher degree of variation in dislocation etch-pit shapes(ellipticities). Conversely, dislocation clusters exhibiting the lowest recombination strength containmostly dislocations with identical line vectors, resulting in very similar etch-pit shapes. Thedisorder of dislocation line vector in high-recombination clusters appears to be correlated withimpurity decoration, possibly the cause of the enhanced recombination activity. Based on ourobservations, we conclude that the relative recombination activity of different dislocation clustersin the device may be predicted via an optical inspection of the distribution and shape variation ofdislocation etch pits in the as-grown wafer.

  • 25.
    Chavhan, Sudam D.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Abellon, Ruben D.
    Dept. of Chemical Engineering, Technische Universiteit Delft, The Netherlands.
    Savenije, Tom J.
    Dept. of Chemical Enginering, Technische Universiteit Delft, The Netherlands.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Photovoltaic Study of p-type NiO/PC70BM Hybrid Solar Cells2011Conference paper (Refereed)
    Abstract [en]

    Generally, hybrid solar cells are fabricated by using electron donating conducting polymers or molecules and electron accepting inorganic material e.g. metal oxide nanoparticles, such as TiO2, ZnO or SnO2. Inorganic metal oxides posses interesting physical properties like high electron mobility, transparency in the visible spectrum and high dielectric constant. However, there are very few reports on hybrid solar cells fabricated with p-type metal oxide and n-type organic molecules. We have studied photovoltaic properties of bilayer hybrid solar cells constituted of p-type NiO and [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) molecule. The thin films of NiO were prepared on fluorine doped SnO2 (FTO) substrates by RF sputtering in Ar/O2 mixture atmosphere. To fabricate hybrid solar cells, a PC70BM solution was spin coated on top of the smooth and uniform layer of NiO, having thickness of 90 nm. Current-voltage characteristics were measured in dark and under illumination with monochromatic light of wavelength 460 nm and an incident illumination power of 9 mW/cm2. A short circuit current density of 0.15 mA/cm2, open circuit voltage of 0.23 V, and fill factor of 0.26 were found. To understand the photovoltaic mechanism of this type of hybrid solar cells we studied also the bulk heterojunctions made up of p-type NiO nanoparticles with different PCBM molecules.

  • 26.
    Chavhan, Sudam D.
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Solution Processed NiO Hole Transporting Layer in P3HT:PCBM Bulk Heterojunction Organic Solar Cells2011Conference paper (Refereed)
    Abstract [en]

    Despite of low fabrication cost and flexibility, limited life time is the major disadvantage of bulk heterojunction organic solar cells (OSCs). The main causes of short life time of OSCs is the degradation of active layer in presence of light and O2 and the effect of the acidic PEDOT:PSS on the ITO electrode. To overcome this problem PEDOT: PSS can be replaced by a p-type metal oxide hole transportation layer, such as NiO. There are reports on vacuum deposited NiO hole transporting layers in OSCs. Here, we have used the low-cost spin coating technique to deposit the NiO layer from a dispersion of NiO particles in methanol. Concentration and deposition parameters were optimized to obtain 40-50 nm thick layer of NiO as observed by tapping mode atomic force microscopy. The device performance of P3HT:PCBM solar cell with ITO/PEDOT: PSS and ITO/NiO electrodes was compared.

  • 27.
    Cirillo, E.N.M.
    et al.
    Univ Roma La Sapienza, Dipartimento Sci Base & Applicate Ingn, Rome, Italy.
    Krehel, O.
    Eindhoven Univ Technol, Inst Complex Mol Syst, Eindhoven, Netherlands.
    Muntean, Adrian
    Eindhoven Univ Technol, Inst Complex Mol Syst.
    van Santen, R.
    Eindhoven Univ Technol, Inst Complex Mol Syst, Eindhoven, Netherlands.
    Sengar, A.
    Indian Inst Technol Delhi, Delhi, India.
    Residence time estimates for asymmetric simple exclusion dynamics on strips2015In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 442, p. 436-457Article in journal (Refereed)
  • 28.
    Dzwilewski, Andrzej
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    The effect of light exposure on P3HT:PCBM films: a NEXAFS study2011Conference paper (Refereed)
    Abstract [en]

    A simple photolithography method was developed for patterning organic field effect transistors (OFETs) prepared from blends of poly(3-hexylthiophene), P3HT, and [6,6]-phenyl-C61-butyric acid methyl ester, PCBM.(1) This Photo-induced and Resist-free Imprint patterning (PRI) technique allows also the single solution step production of organic CMOS circuits.(2) It consists of two subsequent processing steps: 1) exposure: photo-irradiation of the P3HT:PCBM blend by visible laser light and 2) development: rinsing of the film in an organic solvent mixture that is selective for PCBM. As a result, two electronically different materials are obtained, i.e. the exposed and developed (ED) material, and the unexposed and developed (UD) material. The method is based on the modification of the PCBM component in the irradiated area, which becomes effectively insoluble in the solvent mixture, while the PCBM in the non-irradiated area is removed during development. Therefore, we expect that the UD material is pure P3HT, a hypothesis that is confirmed by the p-type conductivity of the ED region. Near-Edge X-ray Absorption Fine Structure spectroscopy (NEXAFS) was used to determine the surface composition of these films. C K-edge NEXAFS spectra of pristine, photo-exposed, and developed blend films, as well as films of the pure components were measured at the synchrotron facility MAX-lab in Lund, Sweden. The spectra for P3HT and PCBM are significantly different and the components can be clearly distinguished in the blend spectra. From the relative intensities of the P3HT and PCBM peaks, the actual blend composition can be estimated, both on the surface, using partial electron yield (PEY), and deeper in the sub-surface region of the film, using total electron yield (TEY). From the similarity of the spectra of the UD blend sample and the pure P3HT sample, we conclude that the remaining material after washing the pristine blend is indeed P3HT, and the ED blend sample retains its two-component character. The surface composition of the blend films is significantly more polymer-rich than the bulk blend ratio used to prepare the film. Both for the pristine blend and the photo-exposed blend differences are observed between the PEY and TEY spectra, indicating the existence of a polymer-enriched surface. Such gradients in thin films of P3HT:PCBM blends have been observed by others using variable-angle spectroscopic ellipsometry,(3) NEXAFS,(4) and neutron reflectometry,(5) and also in other polymer:PCBM blends by dynamic secondary ion mass spectrometry (d-SIMS).(6)

    References (1) Dzwilewski, A.; Wagberg, T.; Edman, L. J. Am. Chem.Soc. 2009, 131, 4006. (2) Dzwilewski, A.; Matyba, P.; Edman, L. J. Phys. Chem. B 2010, 114, 135. (3) Campoy-Quiles, M., et al., Nature Materials 2008, 7,158-164 (4) Germack,D.S. et al., Appl. Phys. Lett. 2009, 94, 233303. (5) Kiel, J.W. et al., Soft Matter 2010, 6, 641-646. (6) Björström, C.M. et al, J. Phys.: Condens. Matter 2005, 17, L529-L534.

  • 29.
    Dzwilewski, Andrzej
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Light induced effects in PCBM:P3HT blend films2012In: Hybrid and Organics Photovoltaics Conference: Uppsala, Sweden, 2012 / [ed] Anders Hagfeldt, SEFIN, Castelló (Spain), 2012, p. 155-155Conference paper (Refereed)
  • 30.
    Dzwilewski, Andrzej
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zharnikov, Michael
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    X-ray absorption study of light induced effects in PCBM:P3HT blend films2011In: Photovoltaics at the nanoscale: Hasselt University (Belgium) 24-28 October 2011, Hasselt University, Belgium, 2011, p. 59-59Conference paper (Refereed)
  • 31. Díaz-Herrera, B.
    et al.
    Montesdeoca-Santana, Amada
    Jiménez-Rodriguez, E.
    González-Díaz, B.
    Hernández Rodríguez, C.
    Guerrero-Lemus, Ricardo
    Rinio, Markus
    Borchert, Dietmar
    Upgraded metallurgical grade silicon for solar cell fabrication2009Conference paper (Other academic)
  • 32.
    Edvardsson, Elisabet
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Band structures of topological crystalline insulators2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Topological insulators and topological crystalline insulators are materials that have a bulk band structure that is gapped, but that also have toplogically protected non-gapped surface states. This implies that the bulk is insulating, but that the material can conduct electricity on some of its surfaces. The robustness of these surface states is a consequence of time-reversal symmetry, possibly in combination with invariance under other symmetries, like that of the crystal itself. In this thesis we review some of the basic theory for such materials. In particular we discuss how topological invariants can be derived for some specific systems. We then move on to do band structure calculations using the tight-binding method, with the aim to see the topologically protected surface states in a topological crystalline insulator. These calculations require the diagonalization of block tridiagonal matrices. We finish the thesis by studying the properties of such matrices in more detail and derive some results regarding the distribution and convergence of their eigenvalues.

  • 33.
    Ekhagen, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Silicon solar cells: basics of simulation and modelling: Using the mathematical program Maple to simulate and model a silicon solar cell2017Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The main goal of this thesis was to simulate a solar cell with the symbolic manipulation tool Maple and discuss the strength and weaknesses of using Maple instead of the already known simulation program PC1D. This was done mainly by solving the three essential differential equations governing the current density and excess electron and hole densities in the solar cell. This could be done easily by using known simplifications especially the low injection assumption. However it was also a success without using this particular simplification but the solutions had to be achieved using a numerical method instead of direct methods. The results were confirmed by setting up the same solar cell with PC1D. The conclusion is that Maple gives the user increased freedom when setting up the solar cell, however PC1D is easier to use if this freedom is not needed. At the end of this thesis a brief introduction is also made on the possibility of using Maple with a tandem cell setup instead of single junction.

  • 34.
    Ericsson, Leif K E
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Magnusson, Kjell
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Zhang, Hanmin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    AFM and STM Study of ZnO NanoplatesManuscript (preprint) (Other academic)
    Abstract [en]

    The surface morphology and electronic structure of hexagonal ZnO nanoplates have been studied by Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM). It was found that these nanoplates are terminated by their polar (0001) surfaces. The AFM investigation was performed in the ambient conditions with the nanocrystals “as grown”. Surprisingly, the AFM images of the top surfaces revealed an interesting triangular reconstruction, which was earlier observed only after cycles of sputtering and annealing of the ZnO(0001) surface in Ultra High Vacuum (UHV) systems. The surface atomic and electronic structures of these nanoplates have been further studied by STM and Scanning Tunneling Spectroscopy (STS) in UHV. The STM images also showed a triangular structure with single atomic steps. In addition, a 2x2 surface reconstruction has been observed with high resolution STM. This reconstruction agrees well with the recently proposed model that involves the removal of 1/4 of the topmost Zn atoms on the ZnO(0001) surface.

  • 35.
    Ericsson, Leif KE
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Growth and Characterization of ZnO Nanocrystals2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The understanding of surfaces of materials is of crucial importance to all of us. Considering nanocrystals (NCs), that have a large surface to bulk ratio, the surfaces become even more important. Therefore, it is important to understand the fundamental surface properties in order to use NCs efficiently in applications. In the work reported in this thesis ZnO NCs were studied.

    At MAX-lab in Lund, synchrotron radiation based Spectroscopic Photoemission and Low Energy Electron Microscopy (SPELEEM) and X-ray Photoelectron Spectroscopy (XPS) were used. At Karlstad University characterization was done using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), Scanning Tunnelling Microscopy (STM), Auger Electron Spectroscopy (AES), and XPS.

    The fundamental properties of ZnO surfaces were studied using distributions of ZnO NCs on SiO2/Si surfaces. The conditions for distribution of ZnO NCs were determined to be beneficial when using ethanol as the solvent for ultrasonically treated dispersions. Annealing at 650 °C in UHV cleaned the surfaces of the ZnO NCs enough for sharp LEEM imaging and chemical characterization while no sign of de-composition was found. A flat energy band structure for the ZnO/SiO2/Si system was proposed after 650 °C. Increasing the annealing temperature to 700 °C causes a de-composition of the ZnO that induce a downward band bending on the surfaces of ZnO NCs.

    Flat ZnO NCs with predominantly polar surfaces were grown using a rapid microwave assisted process. Tuning the chemistry in the growth solution the growth was restricted to only plate-shaped crystals, i.e. a very uniform growth. The surfaces of the NCs were characterized using AFM, revealing a triangular reconstruction of the ZnO(0001) surface not seen without surface treatment at ambient conditions before. Following cycles of sputtering and annealing in UHV, we observe by STM a surface reconstruction interpreted as 2x2 with 1/4 missing Zn atoms.

  • 36.
    Ericsson, Leif
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Magnusson, Kjell
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Microwave assisted rapid growth of flat ZnO(0001) platelets2013Manuscript (preprint) (Other academic)
  • 37.
    Fenning, D. P.
    et al.
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA .
    Hofstetter, Jasmin
    Instituto de Energía Solar, Universidad Politécnica de Madrid, 28040 Madrid, Spain .
    Bertoni, M. I.
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA .
    Hudelson, S.
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA .
    Rinio, Markus
    Laboratory and Service Center, Fraunhofer Institute for Solar Energy Systems (ISE), 45884 Gelsenkirchen, Germany .
    Lelièvre, J. F.
    Ctr Tecnol Silicio Solar CENTESIL, Getafe 28905, Spain.
    Lai, B.
    Argonne Natl Lab, Adv Photon Source, Argonne, IL 60439 USA.
    del Cañizo, C.
    Univ Politecn Madrid, Inst Energia Solar, E-28040 Madrid, Spain.
    Buonassisi, Tonio
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA .
    Iron distribution in silicon after solar cell processing: Synchrotron analysis and predictive modelling2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, p. 162103-Article in journal (Refereed)
    Abstract [en]

    The evolution during silicon solar cell processing of performance-limiting iron impurities isinvestigated with synchrotron-based x-ray fluorescence microscopy. We find that during industrialphosphorus diffusion, bulk precipitate dissolution is incomplete in wafers with high metal content,specifically ingot border material. Postdiffusion low-temperature annealing is not found to alterappreciably the size or spatial distribution of FeSi2precipitates, although cell efficiency improvesdue to a decrease in iron interstitial concentration. Gettering simulations successfully modelexperiment results and suggest the efficacy of high- and low-temperature processing to reduce bothprecipitated and interstitial iron concentrations, respectively.

  • 38.
    Ghavanini, Farzan
    et al.
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Jackman, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lundgren, Per
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Enoksson, Peter
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, 41296 Göteborg, Sweden.
    Direct measurement of bending stiffness and estimation of Young’s modulus of vertically aligned carbon nanofibers2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 19Article in journal (Refereed)
    Abstract [en]

    We have measured the bending stiffness of as-grown vertically aligned carbon nanofibers using atomic force microscopy inside a scanning electron microscope. We show that the assumption of a uniform internal structure is inadequate in describing nanofibers mechanical properties and that a dual phase model is needed. We present a model in which different Young’s moduli are assigned to the inner graphitic core and the outer amorphous carbon shell and show that it provides a better fit to the measurements. We obtain values of 11±8 GPa and 63±14 GPa for the Young’s modulus of the inner core and the outer shell, respectively.

  • 39.
    Ghavanini, Farzan
    et al.
    Chalmers University of Technology.
    Jackman, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Lundgren, Per
    Chalmers University of Technology.
    Enoksson, Peter
    Chalmers University of Technology.
    Direct Measurement of the Young’s Modulus of Individual Vertically Aligned Carbon Nanofibers (VACNFs)2011Conference paper (Refereed)
    Abstract [en]

    Vertically aligned carbon nanofibers (VACNFs) are synthesized in a plasma-enhanced chemical vapor deposition process (PECVD) in which the position, diameter, length, and alignment of individual nanofibers can be controlled accurately. This has provided an unprecedented opportunity to realize a new bottom-up-engineered material with excellent mechanical and electrical properties which could exploit the third dimension at a reasonable cost. VACNFs have been already employed in a number of applications including electron emitters, gene delivery arrays, and nanoelectromechanical systems. However, no direct measurement of the Young’s modulus of VACNFs has been reported yet. Qi et al. have used nanoindentation method to measure the collective response of a forest of VACNFs with a distribution in length and diameter of the constituent nanofibers. Kaul et al., have reported in situ uniaxial compression tests on individual VACNFs but they have not provided enough information to evaluate the accuracy of their measurements. Indirect estimation of the VACNFs Young’s modulus has also been reported by Eriksson et al. from measurements of the resonance frequency of a nanofiber deposited on top of an excitation electrode. Here, we report on direct measurements of VACNFs Young’s modulus using a piezoresistive atomic force microscope (AFM) cantilever implemented inside a scanning electron microscope (SEM). The VACNFs were grown from Ni catalyst seeds, patterned using electron-beam lithography on top of a stoichiometric TiN underlayer. The VACNFs were grown in a commercially available PECVD chamber (AIXTRON BlackMagic™). The nanofibers were approached from the side and pushed at the tip (resembling a cantilever beam) and force-deflection curves were obtained. By calibrating the AFM sensor the bending stiffness of the nanofiber could be determined. The Young’s modulus was then estimated by taking the nanofibers dimensions into account. The sub-nano Newton force precision provided by the AFM force-sensor together with the fact the individual VACNFs could be observed in the SEM simultaneously during the measurements, has enabled us to measure the nanofibers Young’s modulus with a high precision. Preliminary measurements indicate that VACNFs posses a Young’s modulus between 40 to 100 GPa which is comparable to CVD grown carbon nanotubes of similar diameter

  • 40.
    Gurnett, Michael
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Holleboom, Thijs
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Photoemission study of the Li/Ge(111)-3×1 reconstruction2009In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, ISSN 0039-6028, Vol. 603, no 4, p. 727-735Article in journal (Refereed)
    Abstract [en]

    In this article we report our findings on the electronic structure of the Li induced Ge(1 1 1)–3 × 1reconstruction as determined by angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and core-level spectroscopy using synchrotron radiation. The results are compared to the theoretical honeycomb-chain-channel (HCC) model for the 3 × 1reconstruction as calculated using density functional theory (DFT). ARUPS measurements were performed in both the and directions of the 1 × 1 surface Brillouin zone at photon energies of 17 and 21.2 eV. Three surface related states were observed in the direction. In the direction, at least two surface states were seen. The calculated band structure using the single-domain HCC model for Li/Ge(1 1 1)–3 × 1 was in good agreement with experiment, allowing for the determination of the origin of the experimentally observed surface states. In the Ge core-level spectra, two surface related components were identified, both at lower binding energy with respect to the Ge bulk peak. Our DFT calculations of the surface core-level shifts were found to be in fair agreement with the experimental results. Finally, in contrast to the Li/Si(1 1 1)–3 × 1 case, no double bond between Ge atoms in the top layer was found

  • 41.
    Haarahiltunen, Antti
    et al.
    Aalto University.
    Yli-Koski, Marko
    Aalto University.
    Talvitie, Heli
    Aalto University.
    Vähänissi, Ville
    Aalto University.
    Lindroos, Jeanette
    Aalto Universitet, Dept Micro & Nanoscience.
    Savin, Hele
    Aalto University.
    Gettering of iron in CZ-silicon by polysilicon layer2011In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 8, no 3, p. 751-754Article in journal (Refereed)
  • 42. Hahn, Giso
    et al.
    Zechner, C.
    Rinio, Markus
    Fath, Peter
    Willeke, G.
    Bucher, E.
    Enhanced Carrier Collection observed in Mechanically Structured Silicon with Small Diffusion Length1999In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 86, no 12, p. 43-47 mflArticle in journal (Refereed)
    Abstract [en]

    The diffusion length of minority charge carriers in the silicon bulk Ldiffis an important characteristicof optoelectronic devices fabricated from low cost silicon wafers. In this study computer simulationshave been carried out to calculate the beneficial effects of a macroscopic surface texturization on thecharge carrier generation and the collection probability. Textured solar cells should be able tocollect charge carriers more effectively resulting in an increased current due to the special emittergeometry resulting from the texture, decreased reflection losses, and the inclined penetration of thelight. In order to prove this expected behavior, deeply V-textured solar cells have been processedand characterized on low cost silicon reaching an Ldiffof about 25 mm. Spatially resolved highresolution measurements of the internal quantum efficiency exhibit a strongly increased signal in thetexture tips which is the first experimental proof of the increased charge carrier collectionprobability of deeply textured solar cells. This effect can further be seen in cross sectional electronbeam induced current measurements and the mechanical texture results in an overall gain in shortcircuit current density of about 11% and in efficiency of about 8% relatively.

  • 43.
    Hansson, Rickard
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ericsson, Leif K.E.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Holmes, Natalie P.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Opitz, Andreas
    Department of Physics, Humboldt-Universit¨at zu Berlin, 12489 Berlin, Germany.
    Campoy-Quiles, Mariano
    Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra, 08193, Spain.
    Wang, Ergang
    Chalmers University of Technology, 41296 Göteborg, Sweden.
    Barr, Matthew G.
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Kilcoyne, A. L. David
    Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
    Zhou, Xiaojing
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Dastoor, Paul
    Centre for Organic Electronics, University of Newcastle, Callaghan, NSW 2308, Australia.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Vertical and lateral morphology effects on solar cell performance for a thiophene–quinoxaline copolymer:PC70BM blend2015In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 3, p. 6970-6979Article in journal (Refereed)
  • 44.
    Hirvonen Grytzelius, Joakim
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Thin Mn silicide and germanide layers studied by photoemission and STM2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The research presented in this thesis concerns experimental studies of thin manganese silicide and germanide layers, grown by solid phase epitaxy on the Si(111)7×7 and the Ge(111)c(2×8) surfaces, respectively. The atomic and electronic structures, as well as growth modes of the epitaxial Mn-Si and Mn-Ge layers, were investigated by low-energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), core-level spectroscopy (CLS), and scanning tunneling microscopy and spectroscopy (STM and STS). The magnetic properties of the Mn-Ge films were investigated by X-ray magnetic circular dichroism (XMCD).

    The Mn-Si layers, annealed at 400 °C, showed a √3×√3 LEED pattern, consistent with the formation of the stoichiometric monosilicide MnSi. Up to 4 monolayers (ML) of Mn coverage, island formation was observed. For higher Mn coverages, uniform film growth was found. Our results concerning morphology and the atomic and electronic structure of the Mn/Si(111)-√3×√3 surface, are in good agreement with a recent theoretical model for a layered MnSi structure and the √3×√3 surface structure.

    Similar to the Mn-Si case, the grown Mn-Ge films, annealed at 330 °C and 450 °C, showed a √3×√3 LEED pattern. This indicated the formation of the ordered Mn5Ge3 germanide. A strong tendency to island formation was observed for the Mn5Ge3 films, and a Mn coverage of about 32 ML was needed to obtain a continuous film. Our STM and CLS results are in good agreement with the established model for the bulk Mn5Ge3 germanide, with a surface termination of Mn atoms arranged in a honeycomb pattern. Mn-Ge films grown at a lower annealing temperature, 260 °C, showed a continuous film at lower coverages, with a film structure that is different compared to the structure of the Mn5Ge3 film. XMCD studies showed that the low-temperature films are ferromagnetic for 16 ML Mn coverage and above, with a Curie temperature of ~250 K.

  • 45.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Coverage dependence and surface atomic structure of Mn/Si(111)-√3×√3 studied by scanning tunneling microscopy and spectroscopy2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, p. 235324-1-235324-6Article in journal (Refereed)
    Abstract [en]

    Thin manganese silicide films of different thicknesses on Si(111) have been studied in detail by low-energy electron diffraction (LEED), scanning tunneling microscopy, and scanning tunneling spectroscopy (STM/STS). Up to a Mn coverage of 3–4 monolayers (ML), island formation is favored. For higher Mn coverages up to 12 ML uniform film growth is found. The silicide film morphology at low coverages supports a layered Mn-Si film structure. The silicide surfaces displayed a √3×√3 LEED pattern. STM images recorded from the √3×√3 surfaces mostly show a hexagonal pattern but a honeycomb pattern has also been observed. A surface atomic structure based on chained Mn triangles is proposed. Our STM results are in good agreement with a recent theoretical model. The high-quality STS spectra recorded from the different surfaces show a clear metallic character at 1.5 ML and higher coverages. The filled-state features in the STS spectra at surfaces with 3–4 ML Mn coverages are similar to earlier published angle-resolved photoelectron spectroscopy data.

  • 46.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Mn5Ge3 film formation on Ge(111)c(2×8)2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 86, no 12, p. 125313-1-125313-7Article in journal (Refereed)
    Abstract [en]

    Thin manganese germanide films with different thicknesses on Ge(111) have been studied in detail by low-energy electron diffraction (LEED), scanning tunneling microscopy, and core-level spectroscopy (CLS). Annealing of the deposited Mn on Ge(111)c(2×8) between 330-450 C resulted in well-ordered Mn5Ge3 surfaces as seen by intense 3×3 LEED spots. Up to a coverage of 24 monolayers (ML), island formation is favored. At a coverage of 32 ML a well ordered Mn5Ge3 film was found to fully cover the surface. High-resolution Ge 3d CLS spectra were recorded with photon energies between 50 and 110 eV at normal and 60 emission angles. In contrast to earlier results, three components have been used in the line-shape analysis to achieve a consistent fit over the energy and angular range. In addition, three components have been identified for the Mn 2p CLS spectra. The two major components fit well with a layered Mn germanide structure suggested in the literature.

  • 47.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Surface atomic and electronic structure of Mn5Ge3 on Ge(111)2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, ISSN 1098-0121, Vol. 84, no 19, p. 195306-1-195306-6Article in journal (Refereed)
    Abstract [en]

    The atomic and electronic structure of the Mn5Ge3(001) surface grown on Ge(111) c(2×8) has been studied in detail by angle-resolved photoelectron spectroscopy (ARPES), scanning tunneling microscopy (STM), and scanning tunneling spectroscopy. ARPES spectra recorded from the Γ̅ -K̅ -M̅ and Γ̅ -M̅ -Γ̅ directions of the surface Brillouin zone show six surface-related features. The STM images recorded at biases higher/lower than ±0.4 V always show a honeycomb pattern with two bright protrusions in each unit cell. At lower biases, a hexagonal, intermediate transition, and a honeycomb pattern are observed. These can be explained as arising from Mn and Ge atoms in the sublayer arranged in triangular structures and Mn atoms in the top layer arranged in a honeycomb structure, respectively. The photoemission and STM data from the germanide surface are discussed and compared to earlier published theoretical, photoelectron spectroscopy, and scanning tunneling microscopy studies.

  • 48.
    Hirvonen Grytzelius, Joakim
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Zhang, Hanmin
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Johansson, Lars
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Surface electronic structure of Mn/Si(111)-√3×√32008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 15, p. 155406-1-155406-6Article in journal (Refereed)
    Abstract [en]

    The Mn/Si(111)-√3×√3 surface has been studied in detail by low energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), and core-level photoelectron spectroscopy (CLS). Annealing of the deposited manganese resulted in a well-ordered surface as seen by intense √3×√3 LEED spots. ARPES spectra recorded in the Γ̅ -K̅ -M̅ direction of the √3×√3 surface Brillouin zone show five surface related features in the band gap while in the Γ̅ -M̅ -Γ̅ direction four surface features are observed. The high-resolution Si 2p CLS data were recorded at photon energies between 108–140 eV both at normal and 60° emission angle. The bulk component was identified from the bulk sensitive spectrum recorded at a photon energy of 108 eV. To achieve a consistent core-level fitting over the whole energy and angular range, five components were introduced in the line-shape analysis. The photoemission data from the √3×√3 surface have been discussed and compared with a recent theoretical model. The findings here support a layered Mn silicide film structure.

  • 49. Horzel, Jörg
    et al.
    Seidl, A.
    Buss, W.
    Westram, I.
    Mosel, F.
    Guenther, S.
    Novak, J.
    Sticksel, J.
    Blendin, G.
    Jahn, M.
    Rinio, Markus
    von Campe, H.
    Schmidt, W.
    Inherent material quality advantages for thin EFG si solar cells compared to thick EFG si solar cells2007Conference paper (Other academic)
  • 50.
    Hörmann, Ulrich
    et al.
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Lorch, Christopher
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Hinderhofer, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gerlach, Alexander
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Gruber, Mark
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Kraus, Julia
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Sykora, Benedikt
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Grob, Stefan
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Linderl, Theresa
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Wilke, Andreas
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany.
    Opitz, Andreas
    Department of Physics, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
    Hansson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Ozawa, Yusuke
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Nakayama, Yasuo
    Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Ishii, Hisao
    Center for Frontier Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan and Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
    Koch, Norbert
    Department of Physics, Humboldt University of Berlin, Brook-Taylor-Straße 15, 12489 Berlin, Germany and Helmholtz-Zentrum Berlin für Materialien und Energie GmbH - BESSY II, Albert-Einstein-Straße 15, 12489 Berlin, Germany.
    Moons, Ellen
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Schreiber, Frank
    Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany.
    Brütting, Wolfgang
    Institute of Physics, University of Augsburg, Universitätsstraße 1, 86135 Augsburg, Germany.
    Voc from a Morphology Point of View: the Influence of Molecular Orientation on the Open Circuit Voltage of Organic Planar Heterojunction Solar Cells2014In: Journal of physical chemistry C, ISSN 1932-7455, Vol. 118, no 46, p. 26462-26470Article in journal (Refereed)
    Abstract [en]

    The film morphology and device performance of planar heterojunction

    solar cells based on the molecular donor material α-sexithiophene (6T) are investigated.

    Planar heterojunctions of 6T with two different acceptor molecules, the C60 fullerene and

    diindenoperylene (DIP), have been prepared. The growth temperature of the 6T bottom

    layer has been varied between room temperature and 100 °C for each acceptor. By means

    of X-ray diffraction and X-ray absorption, we show that the crystallinity and the molecular

    orientation of 6T is influenced by the preparation conditions and that the 6T film

    templates the growth of the subsequent acceptor layer. These structural changes are

    accompanied by changes in the characteristic parameters of the corresponding

    photovoltaic cells. This is most prominently observed as a shift of the open circuit

    voltage (Voc): In the case of 6T/C60 heterojunctions, Voc decreases from 0.4 to 0.3 V,

    approximately, if the growth temperature of 6T is increased from room temperature to 100

    °C. By contrast, Voc increases from about 1.2 V to almost 1.4 V in the case of 6T/DIP solar

    cells under the same conditions. We attribute these changes upon substrate heating to

    increased recombination in the C60 case while an orientation dependent intermolecular coupling seems to change the origin of the photovoltaic gap in the DIP case.

123 1 - 50 of 128
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